Ranges of diopter measurement 0 - ?5D Minimum scale value 0.125D at 0 - ?D 0.25D at ?D - ?5D Astigmatism axis of cylinder lens 0-180? Minimum scale value 5? Prism diopter at 1 interval in the range of 0 - 5 at 1 interval in the range of 0 - 20 Prism base angle 0-180? Minimum scale value 5? Regulation of ocular visibility ?D Size of lens ?6mm - ?0mm Overall dimensions of device 275mm?30mm?55mm Weight 5.6kg Lighting lamp 220V15W 110V15W